Hello, 
Thanks for the query to H.C.M.Forum.
If diarrhea is more than 4 weeks ,we call it 
CHRONIC DIARRHEA  as you mentioned in your query.
However , there are so may causes of chronic diarrhea,
Laxatives type of food,
bacterial infection,
Fistula,
Celiac disease,
Crohn's disease,
Infections due to virus,bacteria,parasites,
Cancer,
Certain drugs also develops chronic diarrhea,
 Consistency of fecal matter will reveal whether it is diarrhea or not.
If watery type stool, we call it diarrhea. 
If semisolid or soft stool than causes are others and one of them is 
Anxiety and tension, ( most common cause).
Stomach pain may be due to hyper acidity ( 
gastritis).
Over feeding is  another  cause which is responsible both stomach pain as well diarrhea, so this thing also keep in mind.
Now consult a physician and get in physical & blood examination which will reveal exact nature of disease. 
Water if contaminated may be another reason.
Hope I have answered your query. 
If further any question I will be happy to help.
Good luck.
Dr. HET